1.) 10 pts. Consider a 3-phase multi-stack variable reluctance stepper motor. Suppose it has a step length (single step) of 15 o . As the rotor is turned, the self inductance varies between 1 and 5 mH. Write an expression for the a-phase self-inductance as a function of rotor position. The only variable in this expression should be the rotor position. A sample (but incorrect) answer is ) 8 cos( 03 .0 05 .0 rm asas L θ + = H. 2.) 10 pts. In the context of a variable reluctance stepper motor, explain why some equilibrium points are unstable. A good approach to answering this question would be to make a sketch and then describe a relevant scenario (one is enough) which illustrates why the equilibrium point is unstable. 3.) 5 pts. Draw two circuits used to drive a variable reluctance stepper motor. List one advantage of each circuit each relative to the other. 4.)

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